Skip to content

Connection Issues

Diagnose and resolve connectivity problems.

Device Cannot Connect

Symptoms: - Device shows "Disconnected" - Timeout errors in logs

Troubleshooting Steps:

  1. Verify Network Connectivity 

    ping <device-ip>
telnet <device-ip> 502

  2. Check Device Configuration

  3. Correct IP address
  4. Correct port (usually 502)
  5. Correct slave/unit ID

  6. Device powered on

  7. Firewall Rules

  8. Allow outbound TCP port 502

  9. Check device firewall settings

  10. Device Availability

  11. Device not busy with other connections
  12. Modbus enabled on device
  13. Check device manual for configuration

MQTT Broker Connection Failed

Symptoms: - "MQTT Disconnected" status - Cannot publish data

Troubleshooting Steps:

  1. Test Broker Connectivity 

    telnet <broker-ip> 1883

  2. Verify Credentials

  3. Username correct
  4. Password correct

  5. Check broker logs

  6. Network Issues

  7. Check firewall rules
  8. Verify broker is running

  9. Test with MQTT client tool

  10. TLS Issues

  11. Verify certificates
  12. Check TLS version compatibility

Intermittent Connections

Symptoms: - Devices connecting/disconnecting frequently - Degraded status

Possible Causes:

  1. Network Instability
  2. Packet loss
  3. High latency

  4. Wireless interference

  5. Device Overload

  6. Too many simultaneous connections
  7. Device too slow to respond

  8. Increase frame delay

  9. Timeout Too Short

  10. Increase device timeout
  11. Reduce polling frequency

Next Steps